Disable dependabot automatic labels (#36203)

Disable dependabot's [automatic
labels](https://docs.github.com/en/code-security/dependabot/working-with-dependabot/dependabot-options-reference#labels--),
we have `actions/labeler` to do this job. After this is merged, I will
delete the labels `dependencies` and `github_actions` that dependabot
had created.

Author: silverwind

.github/dependabot.yml

@@ -2,6 +2,7 @@ version: 2
 
 updates:
   - package-ecosystem: github-actions
+    labels: []
     directory: /
     schedule:
       interval: daily